This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 11-118018, filed Apr. 26, 1999; No. 11-118020, filed Apr. 26, 1999; and No. 11-118022, filed Apr. 26, 1999, the entire contents of which are incorporated herein by reference.
This invention relates to a camera with a blur reducing function, which can start a photographing operation (a film exposure operation in the case of a camera using a film, and an imaging operation in the case of a digital camera) at a time point at which the camera is not greatly shook by hand, and more particularly to a method for determining whether the photographing operation should be started.
There are, so far, lots of proposals for a camera with a blur reducing function, which is adapted to start its exposure operation at a time point at which the camera is not greatly shook by hand.
For example, U.S. Pat. No. 5,790,490 proposes an anti-shake camera wherein the level of hand-shake of the camera is detected, and exposure is started when it is determined that the level of shaking is lower than a predetermined value, i.e. that the shake level of the camera is sufficiently reduced, thereby preventing (reducing) blurring from occurring in a photograph.
The method disclosed in the above US Patent enables reduction in blurring in a photograph. If, however, a long time lag exists due to a mechanical operation of, for example, a shutter until exposure is actually executed after it is determined that the level of shaking reduces and hence that start of exposure is allowable, a high blur reducing effect cannot be obtained.
To avoid this, Japanese Patent Application KOKAI Publications Nos. 5-204012, 5-204013 and 5-204014, for example, disclose a technique for estimating hand-shaking, and determining on the basis of the estimation result whether exposure should be started, thereby enhancing the blur reducing effect.
However, to estimate the state of shaking that will occur after a predetermined period, data on the state of shaking at previous time points are necessary. Therefore, unless such data is accumulated for a predetermined period, shake estimation cannot be executed, and accordingly exposure start determination based on the estimation result cannot be executed. The period required for data accumulation is, for example, about several tens milliseconds, which leads to a long time lag for releasing the camera. It is highly possible that a small amount of shaking will occur during the time lag, and accordingly the photographer may miss the opportunity of starting exposure.
There is one type of photography that is executed while moving a camera. In this photography, shaking or movement inevitably occurs. Therefore, if the anti-shake camera as disclosed in the U.S. Pat. No. 5,790,490 is used for the above photography method, the operation of moving a camera is erroneously determined as shaking. As a result, exposure is hard to start, which may result in missing the best opportunity for photography.
This disadvantage can be eliminated by turning off the blur reducing function or mode. In order to turn off the mode, however, setting/operation for it alone must be done and it is troublesome.
Further, a problem of xe2x80x9cshakingxe2x80x9d, which occurs in usual photography, exists in a direction differing from that of the movement of a camera during photography executed while moving the camera.
In the anti-shake camera disclosed in the US Patent, reduction of shaking is detected by determining whether or not both shake levels in two directions have crossed a level of zero (shake velocity is zero; a stationary state).
In this technique, exposure is basically started after the level of shaking reduces, and hence the release time lag may be longer than in the usual case. The release time lag greatly depends upon the aforementioned predetermined period. Specifically, if the predetermined period is set short, both the shake levels in two directions rarely cross the zero level, resulting in a long release time lag. On the other hand, if the predetermined period is set longer, it is highly possible that both the shake levels in two directions will cross the zero level, and hence that the start of exposure will be determined to be allowable. Accordingly, the release time lag will be short. In this case, however, it is also highly possible that the degree of blurring in an exposed photograph will be high.
In the system disclosed in the above-described US Patent, basically, if the shake level is continuously high, the shake level during exposure is also high. In light of this, if blurring occurs in a photograph even when exposure timing control is executed to reduce blurring, it is desirable that the release time lag be short.
Moreover, there is a method in which exposure start determination is performed at a time point at which the level of shaking is low, and this time point is determined using a predetermined threshold value instead of the zero level. Also in this case, the same problem as above will occur depending upon whether the threshold value is high or low.
The present invention has been developed in light of the above problems and aims to provide a camera with a blur reducing function for detecting a time point at which the level of shaking is low, thereby starting exposure at this time point, the camera being capable of quickly executing exposure start determination without a long time lag and hence being easy to use.
It is another object of the invention to provide a highly usable camera with a blur reducing function, capable of, without a long shutter time lag, even executing photography while moving the camera so as to obtain a best opportunity for photography.
It is yet another object of the invention to provide a camera with a blur reducing function, in which exposure is allowed when the level of shaking is low, the camera being operable with a short release time lag.
According to a first aspect of the present invention, there is provided a camera with a blur reducing function, comprising:
shake detecting/computing means for detecting and computing a shake state of the camera;
exposure start determining means for executing exposure start determination to reduce shaking during exposure, on the basis of an output of the shake detecting/computing means;
exposure means for executing an exposure operation in accordance with a determination result of the exposure start determining means;
exposure-start-determining-method changing means for changing an exposure start determination method used in the exposure start determining means; and
condition setting means for setting a condition used in the exposure-start-determining-method changing means for changing the exposure start determination method used in the exposure start determining means.
According to a second aspect of the present invention, there is provided a camera with a blur reducing function, comprising:
shake detecting/computing means for detecting and computing a shake state of the camera;
shake estimating means for storing an output of the shake detecting/computing means and estimating a level of shaking on the basis of the stored output;
shake information stored state monitoring means for monitoring a shake information stored state of the shake estimating means;
exposure start determining means for executing exposure start determination to reduce shaking during exposure, on the basis of an output of the shake detecting/computing means or an output of the shake estimating means;
exposure means for executing an exposure operation in accordance with a determination result of the exposure start determining means; and
exposure-start-determining-method changing means for changing an exposure start determination method used in the exposure start determining means, on the basis of a monitoring result of the shake information stored state monitoring means.
According to a third aspect of the present invention, there is provided a camera with a blur reducing function, comprising:
a shake detecting section for sampling shake levels of the camera in a time series manner;
a computing section for receiving a predetermined number of shake data items sampled by the shake detecting section in the time series manner, and executing predetermined computation of the shake data items; and
a photography start timing determining section for comparing latest shake data, output from the shake detecting section, with a first determination reference range, and comparing a computation result, when output from the computing section, with a second reference range different from the first reference range, thereby determining on the basis of comparison results whether or not photography should be started.
According to a fourth aspect of the present invention, there is provided a camera with a blur reducing function including a shake detecting section for repeatedly detecting a shake state of the camera, and in which a shake state of the camera is repeatedly detected in response to a releasing operation for instructing start of photography, and photography is started at a time point at which shaking is in a predetermined state, comprising:
a determination reference range setting section for setting first and second reference ranges which are different from each other;
a shake estimating section for estimating a shake state of the camera to be obtained after a predetermined period, on the basis of a predetermined number of shake data items detected by the shake detecting section; and
a photography start timing determining section for comparing latest shake data, output from the shake detecting section, with a first determination reference range until estimation information is output form the shake estimating section, and comparing the estimation information with the second reference range when the estimation information is output, thereby determining on the basis of comparison results whether or not photography should be started.
According to a fifth aspect of the present invention, there is provided a camera with a blur reducing function, comprising:
a shake data sampling section, responsive to a releasing operation, for sampling, in a time series manner, a shake level in each of two directions perpendicular to a photography optical axis of the camera and intersecting each other;
a xe2x80x9cphotography-with-moving-cameraxe2x80x9d determining section for determining, on the basis of an output of the shake data sampling section, whether or not photography is being executed while moving the camera, and invalidating data which is included in the output of the shake data sampling section and concerns a direction in which the camera is moving; and
a control section for starting photography when the output of the shake data sampling section satisfies a predetermined reference value, or when a predetermined period has elapsed after the releasing operation.
According to a sixth aspect of the present invention, there is provided a camera for detecting levels of shaking in a plurality of directions in response to a releasing operation, and starting photography at a time point at which shaking is at a low level, comprising:
a shake level detecting, responsive to a releasing operation, for detecting levels of shaking in a plurality of directions; and
a control section for determining, on the basis of levels of shaking in the plurality of directions detected by the shake level detecting section, whether or not photography is being executed while moving the camera, the control section invalidating a shake state signal obtained in a direction in which photography is being executed while moving the camera.
According to a seventh aspect of the present invention, there is provided a camera with a blur reducing function, comprising:
a time measuring section, responsive to a releasing operation, for starting to measure a time period and stop it when a predetermined time limit expires;
a shake detecting section for repeatedly detecting a shake level of the camera; and
a photography start timing determining section for starting photography, when the predetermined time limit has expired or while time measurement is executed before the predetermined time limit expires, in accordance with a comparison result between a predetermined reference range and an estimated level of shaking which is obtained, after a predetermined period, on the basis of a plurality of shake data items including the detected shake level and shake levels near the detected shake level, wherein
the photography start timing determining section increases the predetermined period each time comparison has been executed.
According to a eighth aspect of the present invention, there is provided a camera with a blur reducing function, comprising:
a time measuring section, responsive to a releasing operation, for starting to measure a time period and stop it when a predetermined time limit expires;
a shake detecting section for repeatedly detecting a shake level of the camera; and
a photography start timing determining section for starting photography, when the predetermined time limit has expired or while time measurement is executed before the predetermined time limit expires, in accordance with a comparison result between a predetermined reference range and an estimated level of shaking which is obtained, after a predetermined period, on the basis of a plurality of shake data items including the detected shake level and shake levels near the detected shake level, wherein
the photography start timing determining section widens the predetermined reference range each time comparison is executed.
According to a ninth aspect of the present invention, there is provided a method of reducing blurring in a photograph taken by a camera which has a sensor for detecting a shake state of the camera and can reduce shaking during exposure, comprising:
a first step of sampling levels of shaking in a time series manner on the basis of an output of the sensor;
a second step of receiving a predetermined number of shake data items sampled in the time series manner, thereby executing predetermined computation of the shake data items;
a third step of comparing latest shake data, output from the sensor, with a first determination reference range;
a fourth step of comparing a computation result, when output at the second step, with a second determination reference range different from the first determination reference range; and
a fifth step of determining, on the basis of a comparison result at the third step or the fourth step, whether or not exposure should be started.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.